Distribuzione spaziale di Aonidiella aurantii (Maskell) su piante di arancio

Specific surveys on within-tree spatial distribution of California red scale, Aonidiella aurantii (Maskell), on orange trees were conducted, to determine the most infested parts of the canopy from where the insect spreads throughout the tree. The following plant organs were sampled: fruits, leaves, green twigs and 3-4 year-old branches from each canopy quadrant (north, east, south, west). Population density of each sample was determined using a microscope. The results were analysed using analysis of variance. Population distribution did not differ significantly among the four quadrants of the canopy. The highest population density occurred on twigs, followed by fruits and then by leaves. The highest insect density observed during the first generation, on 2-3 year-old twigs, indicated a slow movement of California red scale from lignified to green twigs. Therefore, pruning the heavily infested twigs allows to reduce the centres of infestation of A. aurantii population, to create unfavourable microclimatic conditions for population development and to reduce population density using low environmental-impact insecticides.